Question 1

Which four elements make up approximately 96% of the mass of living organisms?

Accepted Answer

Oxygen, Carbon, Hydrogen, Nitrogen

Question 2

An atom has an atomic number of 75 and a mass number of 78. How many neutrons does it have?

Accepted Answer

$$78 - 75 = 3$$ neutrons

Question 3

In ammonia ($$NH_3$$), the bond between nitrogen and hydrogen is best described as:

Accepted Answer

Polar covalent

Question 4

Which property of water is primarily responsible for its ability to move upward through plant vessels against gravity?

Accepted Answer

Cohesion and adhesion due to hydrogen bonding

Question 5

Why is water considered a 'universal solvent'?

Accepted Answer

Its polarity allows it to dissolve many ionic and polar substances

Question 6

Which of the following best explains why oil does not dissolve in water?

Accepted Answer

Oil molecules are nonpolar and hydrophobic

Question 7

A solution has a pH of 5. How many times more hydrogen ions does it have compared to a solution with pH 7?

Accepted Answer

$$10^{(7-5)} = 100$ times more

Question 8

Which statement about hydrogen bonds in water is correct?

Accepted Answer

They are temporary bonds between polar molecules

Question 9

What happens to the pH of pure water when hydrochloric acid ($$HCl) is $$added?

Accepted Answer

pH decreases because $$HCl$$ increases $$[H^+]$$

Question 10

Which of the following best describes the role of buffers in biological systems?

Accepted Answer

Buffers minimize changes in pH by binding excess $$H^+ or$$ $$OH^-$$ ions

Question 11

If sodium hydroxide ($$NaOH) is $$added to water, what is the effect on the $$[OH^-]$$ and pH?

Accepted Answer

$$NaOH$$ increases $$[OH^-]$$ and raises the pH, making the solution more basic

Question 12

Which of the following is an amphipathic molecule?

Accepted Answer

A fatty acid with both hydrophilic and hydrophobic regions

Question 13

Which step in the scientific method involves making a testable statement that can be supported or contradicted by data?

Accepted Answer

Forming a hypothesis

Question 14

A protein folds so that its hydrophobic amino acids are buried inside and hydrophilic amino acids are exposed to water. This is an example of:

Accepted Answer

The influence of amphipathic properties on protein structure

Question 15

Which of the following best describes the dissociation of water?

Accepted Answer

$$H_2O \rightleftharpoons H^+ + OH^-$$

Question 16

What is the pH of pure water at equilibrium?

Accepted Answer

$$pH = 7$$

Question 17

Which of the following is true about acids and bases?

Accepted Answer

Acids increase $$[H^+]$$ and decrease pH; bases increase $$[OH^-]$$ and increase pH

Question 18

Which of the following is a real-world example of water's high surface tension?

Accepted Answer

A water strider walking on the surface of a pond

Question 19

If a buffer is present in a solution and acid is added, what will happen to the pH compared to a solution without a buffer?

Accepted Answer

The pH will decrease less than in the solution without a buffer

Question 20

Which of the following best explains why hydrogen bonds are critical for the properties of water?

Accepted Answer

They allow water molecules to stick together, giving water high cohesion and surface tension

Introduction to General Biology: Elements of Life, Chemical Bonds, Water, and the Scientific Method

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